Certainly not as powerful as common office suites, but https://cryptpad.fr/ is not only open-source but also has already running instance (and has end to end encryption for your documents)

https://syncthing.net/ is a good general file synchronizer. Requires devices too be online simultaneously to sync, but gives you transport encryption with forward secrecy.

It’s probably the best one when it comes to web-based videocalls. I had much better experience with native apps (e.g. Mumble) when it comes to sound quality though.

Original WhatsApp was XMPP with phone number for your username. Pretty much what https://quicksy.im/ does now.

WhatsApp today is completely different beast.

It’s been a year or two, but last time I tried it their app worked fine on x86 Android in qemu. Not the most efficient way to run it, but at least it’s isolated from the rest of the system.

Slight difference is that Zuck has had control from the start, whereas other companies might have had “don’t be evil” leadership that was… optimized away for financial reasons.

Not that it really matters nowadays. Just an observation.